I am making this post strictly for the purpose of helping you to understand just how "finely defined" (detailed) I think.
( "for good, bad, or whatever"

)
The idea of "start in life" and the idea of "origins of glass" are two totally different ideas.
To me - "My start in life" is referring directly to the 'password' itself - "my start in life"
as glass. It does not speak to anything/something that 'glass' (the 'password')
is made from. Before it
is glass, it does
not "have life"
as glass. Therefore, since "my start in life" suggests that it is referring to [the 'password' (itself)] - 'glass' - the whole line suggests that 'glass' starts out as being [often] 'gritty'.
Unless you were to use a phrase like 'I am/was born/made from...' to indicate its "before life" state of existence, 'sand' cannot enter into the meaning of the statement if the 'password' is 'glass'.
In other words, the word 'life' directly implies (or, refers to) the
life of 'glass' (the 'password') and not the
life of 'sand'
in the making of 'glass'.
Again, 'sand' is not part of the
life of 'glass' - it is only a part of what is used to "birth"/make/produce 'glass' -
at which point its "life"
begins as glass.
Never in the
life of 'glass' does it exist
as 'sand'.
And, this is what threw me off - trying to come up with something similar to sand that was gritty - that an artist could "shape" into something 'pretty'.
I hope this makes some kind of sense to you.